Light-emitting device, display apparatus, and electronic system

Abstract

A light-emitting device includes a cathode, an anode, a first light-emitting layer that is disposed between the cathode and the anode and that emits light of a first color, a second light-emitting layer that is disposed between the first light-emitting layer and the cathode and that emits light of a second color different from the first color, and an intermediate layer that is disposed between and in contact with the first light-emitting layer and the second light-emitting layer and that contains a first material and a second material different from the first material. The light-emitting device satisfies inequality (1): LLA−LLB≧0.4 [eV]  (1) wherein LLA [eV] is the energy level of the lowest unoccupied molecular orbital of the first material, and LLB [eV] is the energy level of the lowest unoccupied molecular orbital of the second material.

What is claimed is: 
     
       1. A light-emitting device comprising:
 a cathode; 
 an anode; 
 a first light-emitting layer that is disposed between the cathode and the anode and that emits light of a first color; 
 a second light-emitting layer that is disposed between the first light-emitting layer and the cathode and that emits light of a second color different from the first color; and 
 an intermediate layer that is disposed between and in contact with the first light-emitting layer and the second light-emitting layer and that contains a first material and a second material different from the first material; 
 wherein the light-emitting device satisfies inequality (1):
     LL   A   −LL   B ≧0.4[eV]  (1)
 
 
  wherein LL A  [eV] is the energy level of the lowest unoccupied molecular orbital of the first material, and LL B  [eV] is the energy level of the lowest unoccupied molecular orbital of the second material. 
 
     
     
       2. The light-emitting device according to  claim 1 , wherein
 the second light-emitting layer contains a light-emitting material and a host material that supports the light-emitting material; and 
 the light-emitting device satisfies inequality (2):
     LL   D   −LL   B ≧0.3[eV]  (2)
 
 
  wherein LL D  [eV] is the energy level of the lowest unoccupied molecular orbital of the host material. 
 
     
     
       3. The light-emitting device according to  claim 1 , wherein
 the second light-emitting layer contains a light-emitting material and a host material that supports the light-emitting material; and 
 the light-emitting device satisfies inequality (3):
   | LL   A   −LL   D |≦0.2[eV]  (3)
 
 
  wherein LL D  [eV] is the energy level of the lowest unoccupied molecular orbital of the host material. 
 
     
     
       4. The light-emitting device according to  claim 1 , wherein the light of the second color has a shorter wavelength than the light of the first color. 
     
     
       5. The light-emitting device according to  claim 1 , wherein the first material has a higher electron mobility than the second material. 
     
     
       6. The light-emitting device according to  claim 1 , further comprising a third light-emitting layer that is disposed between the first light-emitting layer and the anode or between the second light-emitting layer and the cathode and that emits light of a third color different from the first and second colors. 
     
     
       7. A display apparatus comprising the light-emitting device according to  claim 1 . 
     
     
       8. An electronic system comprising the display apparatus according to  claim 7 . 
     
     
       9. A light-emitting device comprising:
 a cathode; 
 an anode; 
 a first light-emitting layer that is disposed between the cathode and the anode and that emits light of a first color, the first light-emitting layer containing a first light-emitting material that emits the light of the first color and a first host material that supports the first light-emitting material as a guest material; 
 a second light-emitting layer that is disposed between the first light-emitting layer and the cathode and that emits light of a second color different from the first color; and 
 an intermediate layer that is disposed between and in contact with the first light-emitting layer and the second light-emitting layer and that contains a first material and a second material having a higher hole mobility than the first material; 
 wherein the light-emitting device satisfies inequalities (4) and (5):
   | HL   B   −HL   C   |<|HL   A   −HL   C |  (4)
 
   | HL   A   −HL   C |≧0.3[eV]  (5)
 
 
  wherein HL A  [eV] is the energy level of the highest occupied molecular orbital of the first material, HL B  [eV] is the energy level of the highest occupied molecular orbital of the second material, and HL C  [eV] is the energy level of the highest occupied molecular orbital of the first host material. 
 
     
     
       10. The light-emitting device according to  claim 9 , wherein the second material and the first host material satisfy inequality (6):
   | HL   B   −HL   C |≦0.2[eV]  (6).
 
 
     
     
       11. The light-emitting device according to  claim 9 , wherein the first material has a higher electron mobility than the second material. 
     
     
       12. The light-emitting device according to  claim 9 , wherein the light of the second color has a shorter wavelength than the light of the first color. 
     
     
       13. The light-emitting device according to  claim 9 , wherein the light-emitting device satisfies inequality (7):
     LL   A   −LL   B ≧0.4[eV]  (7)
 
  wherein LL A  [eV] is the energy level of the lowest unoccupied molecular orbital of the first material, and LL B  [eV] is the energy level of the lowest unoccupied molecular orbital of the second material. 
 
     
     
       14. The light-emitting device according to  claim 9 , wherein
 the second light-emitting layer contains a second light-emitting material that emits the light of the second color and a second host material that supports the second light-emitting material; and 
 the light-emitting device satisfies inequality (8):
   | LL   A   −LL   D |≦0.2[eV]  (8)
 
 
  wherein LL A  [eV] is the energy level of the lowest unoccupied molecular orbital of the first material, and LL D  [eV] is the energy level of the lowest unoccupied molecular orbital of the second host material. 
 
     
     
       15. The light-emitting device according to  claim 9 , further comprising a third light-emitting layer that is disposed between the first light-emitting layer and the anode or between the second light-emitting layer and the cathode and that emits light of a third color different from the first and second colors. 
     
     
       16. A display apparatus comprising the light-emitting device according to  claim 9 . 
     
     
       17. An electronic system comprising the display apparatus according to  claim 16 .